1. Field of the Invention
This invention is an apparatus and method for measuring both the resistance and capacitance of the parallel RC circuit that is the equivalent of any substantially non-inductive two-port device.
2. Description of the Prior Art
U.S. Pat. No. 3,668,523 shows a device which measures the voltage dependent capacitance of a metal-insulator-semiconductor; however, this device cannot measure any resistance, such as the dynamic impedance of a photovoltaic diode, as does the present invention. Furthermore, this patent always uses a linear ramp voltage source. Because of this, the patentee requires an X-Y display device such as an oscilloscope to measure his voltage. This is more expensive as well as more difficult to read than in the present invention, where it is possible to use only an inexpensive easy-to-read digital meter to measure capacitance.
U.S. Pat. No. 3,387,211 discloses a complicated circuit which measures only the impedance of a diode.
U.S. Pat. No. 3,614,614 shows a method using a FET and an oscilloscope to measure only the capacitance of a diode.
U.S. Pat. No. 2,779,922 shows circuits using bulky transformers. FIG. 8 shows the use of variable capacitor 56 to measure collector capacitance of transistor 10.
U.S. Pat. No. 3,054,055 uses a bridge to measure resistance, figure of merit, and tangential sensitivity of a diode.
Monticelli et al, "Op-amp circuit measures diode-junction capacitance", Electronics, July 10, 1975, pp. 112-113; and Kaplan et al, "New method of continuously measuring differential capacitance changes", Electronics Letters, vol. 11, no. 15, pp. 333-334, July 24, 1975, measure certain capacitances but not resistances as in the present invention.